Mast cells within tissue have constant relationships with specific structures such as nerves and blood vessels, although the stimuli that govern mast cell migration and homing are incompletely understood. We now report that the receptor CX3CR1 is expressed by cultured murine mast cells and by isolated human dermal mast cells. Fractalkine, a membrane-bound CX3C chemokine expressed by dermal epithelial and dendritric cells, attracts mast cells in vitro. Fractalkine did not lead to mast cell degranulation. It may thus be that fractalkine expression by specific cells within tissues may contribute to tissue-specific homing of mast cells